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Adam H. Monahan and John C. Fyfe

a dipole centered at approximately the latitude of the core of the time-mean jet. This structure is generally interpreted as representing meridional displacements of the eddy-driven jet (the so-called zonal index), while higher-order EOFs (when they are considered) are interpreted as reflecting changes in jet strength or width (e.g., Feldstein and Lee 1998 ; Feldstein 2000 ; DeWeaver and Nigam 2000 ; Codron 2005 ; Vallis et al. 2004 ). Wittman et al. (2005) consider numerical simulations

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Audrey Delpech, Sophie Cravatte, Frédéric Marin, Yves Morel, Enzo Gronchi, and Elodie Kestenare

equator ( Firing et al. 1998 ). In the tropical Pacific, pioneer cruises ( Tsuchiya 1975 ; Eriksen 1981 ; Firing 1987 ; Firing et al. 1998 ; Rowe et al. 2000 ; Gouriou et al. 2001 ) revealed the presence of several persistent zonal currents below the thermocline in the near-equatorial band. Among them, the Tsuchiya jets are eastward currents found in the whole basin just below the thermocline between 2.5° and 5° from the equator, with intensities of 20–40 cm s −1 ( Rowe et al. 2000 ). The North

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Bing Pu and Kerry H. Cook

1. Introduction It has long been recognized that the eastern tropical Atlantic is an important moisture source for West Africa, and that low-level westerlies transport moisture onto the continent in boreal summer ( Lamb 1983 ; Koster et al. 1986 ; Cadet and Nnoli 1987 ; Druyan and Koster 1989 ; Grist and Nicholson 2001 ; Fontaine et al. 2003 ). The westerly flow near 10°N along the West African coast was identified as a jet in satellite-based observations by Grodsky et al. (2003) . Here

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Clemens Spensberger and Thomas Spengler

1. Introduction Jets in the upper troposphere signify regions of strong baroclinicity, a prerequisite for the development of extratropical cyclones (e.g., Lorenz 1955 ; Lindzen and Farrell 1980 ) and storm tracks ( Chang et al. 2002 ; Wirth et al. 2018 ). Jets also demarcate the Rossby waveguide, as they are usually associated with strong gradients in potential vorticity ( Hoskins and Ambrizzi 1993 ; Martius et al. 2010 ). In climate dynamics (e.g., Wallace and Gutzler 1981 ; Limpasuvan

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S. E. Nicholson, A. I. Barcilon, M. Challa, and J. Baum

1. Introduction The tropical easterly jet stream (TEJ) is one of the most intense circulation features over Africa. This jet lies in the upper troposphere and extends from Asia to West Africa, reaching core speeds in excess of 35 m s −1 . It spans some 20°–30° of latitude. Most research on the TEJ has been in the context of the Indian monsoon ( Mishra 1987 ; Chen and Yen 1991 , 1993 ; Chen and van Loon 1987 ). It is considered to be an active player in the monsoon system. Specifically, waves

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Guihua Wang, Dake Chen, and Jilan Su

to the positive wind stress curl prevailing there. Yang and Liu (2003) suggest that the cyclonic eddy off northwest Luzon behaves like a wind-forced Rossby wave. The fact that orographic wind jets normal to a coast can generate eddies has long been known [e.g., see the review of Willett et al. (2006) for eddies off the southeast coast of Tehuantepec, Mexico]. Willett et al. (2006) have also reviewed other mechanisms that may contribute to eddy genesis there. The general picture of the

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Brian A. Colle and David R. Novak

scale larger than a typical sea breeze (i.e., 100–200 km). Such coastal flows may be influenced by differential surface heating and coastal geometry, as well as the Appalachian terrain farther inland ( Fig. 1a ). The goal of this study is to investigate a coastal low-level jet that develops primarily during the spring and summer months, in which relatively strong (>11 m s −1 ) southerly winds occur in the New York Bight (NYB; the offshore region bounded by the northern New Jersey and Long

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J. B. Marston, E. Conover, and Tapio Schneider

; Majda and Wang 2006 ), generally cannot be used in developing statistical closures for such flows. In this paper, we investigate the inhomogeneous statistics of what may be the simplest flow subject to rotation, large-scale forcing, and dissipation that exhibits mixing and no-mixing regions in statistically steady states: barotropic flow on a rotating sphere driven by linear relaxation toward an unstable zonal jet. Depending on a single control parameter, namely the relaxation time, this prototype

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Xiaowei Hong, Riyu Lu, and Shuanglin Li

1. Introduction The summer Asian westerly jet elongates along midlatitude Eurasia over the upper troposphere and is an important component of the atmospheric circulation system. The year-to-year variation of the summer Asian jet reflects the adjustment and interaction of atmospheric circulation, and exerts great influences on climate, particularly over the Eurasian continent. The year-to-year variation of upper-tropospheric zonal winds over Eurasia is inhomogeneous along the zonal direction

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Joseph Kidston, G. K. Vallis, S. M. Dean, and J. A. Renwick

1. Introduction a. Jet stream movement There is evidence of a poleward shift of the eddy-driven jet streams in recent decades, particularly in the Southern Hemisphere ( Feldstein 2002 ; Marshall 2003 ; Ostermeier and Wallace 2003 ; Thompson et al. 2000 ; Trenberth et al. 2007 ). A large portion of the observed mid- to high-latitude temperature trends bear the signature of such a shift ( Hurrell 1996 ; Thompson et al. 2000 ; Thompson and Solomon 2002 ; Trenberth et al. 2007 ). Events such

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